MIC79110
Simple 1.2A Linear Li-Ion Battery Charger
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
October 2007 M9999-102507
General Description
The Micrel MIC79110 is a simple and accurate lithium ion
battery charger. The part features a built-in pass transistor,
precision programmable current limiting (±5%), and
precision voltage termination (±0.75% over temperature).
The MIC79110 packs full functionality into a small space.
Other features of the MIC79110 include two independent
indicators: a digital End-of-Charge signal that is
programmable with a resistor to ground, and an analog
current output that is proportional to the output current,
allowing for monitoring of the actual charging current.
Additional features include very low dropout (550mV over
the temperature range), thermal shutdown, and reverse
polarity protection. In the event the input voltage to the
charger is disconnected, the MIC79110 also provides
minimal reverse-current and reversed-battery protection.
Available in both fixed 4.2V and adjustable outputs, the
MIC79110 is offered in the leadless 10-pin 3mm x 3mm
MLF
®
with an operating junction temperature range of
–40˚C to +125˚C.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
• Input voltage range: 2.5V to 16V
• High output voltage accuracy of ±0.75%
over –5°C to +60˚C
• Current limit ±5% accurate from –5°C T
J
+ 125°C
• Programmable end-of-charge flag
• Analog output proportional to output current
• Adjustable and fixed 4.2V output
• Low dropout voltage of 550mV at 700mA load, over
temperature
• 1.2A max charge current
• Excellent line and load regulation specifications
• Reverse current protection
• Thermal shutdown and current limit protection
• Tiny 10-Pin 3mm × 3mm MLF
®
package
• Junction temperature range: –40°C to +125°C
Applications
• Cellular phones
• PDAs
• Digital cameras
• Camcorders
• MP3 players
• Notebook PCs
• Portable Meters
• Cradle chargers
• Car chargers
• Battery packs
___________________________________________________________________________________________________________
Typical Application
V
IN
SD
R
EOC
R
SET
BAT
SNS
D
EOC
A
CHG
GND
MIC79110
4.2V
Li-Ion
Cell
V
IN
S
HUTDOWN
ENABLE
4.2V
BAT
MIC79110 Typical Application
Micrel, Inc. MIC79110
October 2007 2 M9999-102507
Ordering Information
Part Number
Standard Marking Pb-Free Marking
Voltage Junction
Temp. Range Package
MIC79110-4.2BML L942 MIC79110-4.2YML L942* 4.2V –40° to +125°C 10-pin 3×3 MLF
®
MIC79110BML L9AA MIC79110YML L9AA* Adj. –40° to +125°C 10-pin 3×3 MLF
®
* Pb-Free “Y” indicator is added to the device mark after LOGO.
Pin Configur ation
V
IN
V
IN
5
1SD
R
SET
SNS
BAT
10 GND
R
EOC
D
EOC
A
CHG
9
8
7
2
3
4
6
V
IN
V
IN
5
1SD
R
SET
ADJ
BAT
10 GND
R
EOC
D
EOC
A
CHG
9
8
7
2
3
4
6
Fixed Output
10-Pin 3mm × 3mm MLF
®
(ML) Adjustable Output
10-Pin 3mm × 3mm MLF
®
(ML)
Pin Description
Pin Number Pin Name Pin Function
1 SD Shutdown Input. Logic High = Off; Logic Low = On.
2 RSET
Current limit: Sets constant current limit via an external resistor to ground.
IR
SET
= (0.2V/R
SET
) × 1000.
3 SNS (Fixed voltage only): Sense output, connect directly to battery.
3 ADJ (Adjustable voltage only): Feedback input.
4 BAT Battery Terminal. Connect to single-cell lithium-ion battery.
5, 6 VIN Input supply pin.
7 ACHG
Analog Charge Indicator Output: Current source who’s output current is equal to
1/1000 of the BAT pin current.
8 DEOC
Digital End-of-Charge Output: N-Ch open drain output. Low indicates charging,
a current that is higher than the programmed current set by R
EOC
is charging the
battery. When the current drops to less than the current set by R
EOC
, the output
goes high impedance, indicating end-of-charge.
9 REOC
End-of-Charge Set: Sets end-of-charge current threshold via an external resistor
to ground. I
EOC
= (0.2V/R
EOC
) × 1000.
10 GND Ground
Micrel, Inc. MIC79110
October 2007 3 M9999-102507
Absolute Maximum Ratings(1)
Input Supply Voltage (V
IN
).................................... 0V to 18V
Shutdown Input Voltage (V) ................................. 0V to 10V
Output Voltage (ADJ) .....................................................10V
Power Dissipation ...................................Internally Limited
Junction Temperature ...............................–40°C to +125°C
Operating Ratings(2)
Input Supply Voltage ........................................ 2.5V to 16V
Shutdown Input Voltage (V) ................................... 0V to 7V
Output Voltage (ADJ) ....................................................9.6V
Junction Temperature Range (T
J
)............. –40°C to +125°C
θ
JA
(MLF-10) .......................................................... 60°C
θ
JC
(MLF-10) ............................................................ 2°C
Electrical Characteristics(4)
T
A
= 25°C with V
IN
= V
OUT
+ 1V; I
LOAD
= 100µA; C
BATT
= 10µF; SD = 0V; R
SET
=1k. Bold values indicate –40ºC < T
J
< +125°C; unless
otherwise specified.
Parameter Condition Min Typ Max Units
Output Voltage Accuracy Variation from V
OUT
= 4.2V; T
J
= –5°C to +60°C; I
LOAD
= 50mA -0.75
-1.5
+0.75
+1.5
%
%
ADJ Pin Voltage Accuracy 0.5955 0.6 0.6045 V
Line Regulation V
IN
= V
OUT
+ 1V to 16V @ I
LOAD
= 50mA -0.1 +0.1 %/V
Load Regulation I
LOAD
= 0.1mA to 1A 0.3 %
I
LOAD
= 100mA, R
SET
= 167 160
250 mV
Dropout Voltage(3)
I
LOAD
= 700mA, R
SET
= 167 375
550 mV
I
LOAD
= 10mA, R
SET
= 167 2 3 mA
Ground Current
I
LOAD
= 700mA, R
SET
= 167 24
35 mA
V
IN
Pin Current SD = V
IN
120
300 µA
Shutdown Pin Current SD = 5.2V, V
BAT
= 0 0.1
5 µA
Logic High, regulator off 1.1 V
Shutdown Input Threshold
Logic Low, regulator on
0.9 V
Shutdown Hysteresis 60 mV
Current Limit Accuracy
(4, 5)
V
OUT
= 0.9 × V
NOM
; I
OUT
= 1.2A,
R
SET
= 167, T
J
= –40°C to +85°C
V
OUT
= 0.9 × V
NOM
; I
OUT
= 0.1A,
R
SET
= 2k
-5
-20
+5
+20
%
%
Current Limit Setpoint
Range
(5)
0.1 1.2 A
Maximum Current Limit R
SET
shorted to ground, V
BAT
= 0.9 × V
NOM
1.25 1.65 2.5 A
V
BAT
Reverse Current V
IN
= High impedance or ground 4.2
20 µA
Digital End–of–Charge (D
EOC
) Output
I
EOC (6, 7)
R
EOC
= 4k Current Falling 35
30 50 65
70 mA
mA
I
EOC (6, 7)
R
EOC
= 4k Current Rising 50
40 70 95
100 mA
mA
D
EOC
Logic–Low Voltage I
DEOC
= 5mA, I
BAT
= 700mA 0.74
0.95 V
D
EOC
Leakage Current Logic High = V
IN
= 16V 0.1 µA
D
EOC
On Resistance V
IN
= +5V 150 190
R
EOC
Maximum Current Limit R
EOC
shorted to ground 0.5 1.0 2.0 mA
Analog Charge Indicato r (A
CHG
) Output
I
SOURCE(8)
I
BAT
= 50mA 37 46 55 µA
I
BAT
= 1.2A, T
J
= –40°C to +85°C 800 950 1150 µA
Micrel, Inc. MIC79110
October 2007 4 M9999-102507
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Dropout Voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1V
differential. For outputs below 2.5V, dropout voltage is the input-to-output voltage differential with the minimum input voltage 2.5V. Minimum input
operating voltage is 2.5V.
4. V
NOM
denotes the nominal output voltage.
5. IR
SET
= (0.2V/R
SET
) × 1000
6. Output Current I
EOC
when Digital End-of-Charge output goes high impedance. Currents greater than I
EOC
, the D
EOC
output is low, currents lower
than I
EOC
, D
EOC
is high impedance.
7. I
EOC
= (0.2V/R
EOC
) × 1000
8. I
SOURCE
is the current output from A
CHG
pin. A resistor to ground from the A
CHG
pin will program a voltage that is proportional to the output current.
Block Diagram
V
IN
SD
R
SET
V
REF
BAT
D
EOC
GND
Li-Ion
A
CHG
R
EOC
SNS
Current
Limit Set
End of
Charge
Detect
+
Current
Limit Sense
Shutdown
Control
Thermal
Protection
MIC79110 Block Diagram
Micrel, Inc. MIC79110
October 2007 5
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Typical Characteristics
Micrel, Inc. MIC79110
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Typical Characteristics (continued)
Micrel, Inc. MIC79110
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Functional Characteristics
Micrel, Inc. MIC79110
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Application Information
Detailed Description
The MIC79110 forms a complete charger for 1-cell
Lithium-ion batteries. It includes precision voltage control
(0.75% over temperature) to optimize both cell
performance and cycle life. All are compatible with
common 4.2V Lithium-ion chemistries. Voltages other
than 4.2V can be obtained with the adjustable version.
Other features include current limit, end-of-charge flag
and end-of-charge current limit using an external
resistor. The shutdown pin enables low quiescent
current when not charging.
Current Limit Mode
MIC79110 features an internal current limit that is set by
the RSET pin with a resistor-to-ground. The maximum
current is calculated by the following equation:
IR
set
= (0.2/R
set
) × 1000
Using a 167 R
set
resistor will achieve the maximum
current limit for the MIC79110 at 1.2 amperes.
End of Charge
R
EOC
pin is connected to a resistor-to-ground. This
resistor is used to set the end of charge current for the
lithium ion battery as follows:
IR
EOC
= (0.2/R
EOC
) × 1000
Using a 4k R
EOC
resistor will set the end-of-charge
current at 50mA.
I
REOC
should be set at 10% of the battery’s rated current.
Digital End-of-Charge Output
This pin is the output of an open drain. When tied high to
the supply using a resistor, the output will toggle high or
low depending on the output current of I
BAT
.
• Low state indicates that the I
BAT
current is higher
than the programmed current set by R
EOC
.
• High state indicates that the I
BAT
current is lower
than the programmed current set by R
EOC
. The
output goes high impedance indicating end-of-
charge.
Analog End-Of-Charge Output
The A
CHG
pin provides a small current that is proportional
to the charge current. The ratio is set at 1/1000th of the
output current.
Shutdown
The SD pin serves as a logic input (active low) to enable
the charger.
Built-in hysteresis for the shutdown pin is 50mV over
temperature.
Reverse Polarity Protection
In the event that V
BAT
> V
IN
and the shutdown pin is
active low, there is reverse battery current protection
built in. The current is limited to less than 10µA over
temperature.
Constant Output Voltage/Current Charging
The MIC79110 features constant voltage and constant
current output to correctly charge lithium-ion batteries.
The constant voltage is either 4.2V or adjustable. The
constant current is set by the R
set
pin and is constant
down to around 300mV. Since R
set
can be set below
500mA, the minimum output current is set at 500mA for
output voltages below 100mV. This minimum voltage
starts the charging process in lithium-ion batteries. If the
output current is too low, the battery will not begin
charge.
I Current
evruCI-V01197CIM
I Current 500mA
0.7V
I
MAX
= (0.2/R
SET
)×1000
evruCI-VdradnatS
Lithium Ion Batteries
Lithium-ion batteries are charged in two stages to reach
full capacity. The first stage charges the battery with
maximum charge current until 90% of the battery cell’s
voltage limit is reached. The second stage tops off the
charge with constant voltage charge as the charge
current slowly decreases. End of charge is reached
when the current is less than 3% of the rated current. A
third stage will occasionally top off with charge with
constant voltage charge if the battery voltage drops
below a certain threshold.
Micrel, Inc. MIC79110
October 2007 9
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All lithium-ion batteries take approximately 3 hours to
charge with the second stage taking twice as long as the
first stage. Some chargers claim to be fast chargers by
skipping the second stage and just charges the battery
until the cell voltage is reached. This only charges the
battery to 70% capacity.
An increase in the charge current during stage 1 does
not shorten the total charge time. It will only shorten the
time for stage 1 to complete and lengthen the time in
stage 2.
The lithium-ion loses charge due to aging whether it is
used or not. Do not store the batteries at full charge and
high heat because it will accelerate the aging process.
Try and store with 40% charge and in a cool
environment.
Lithium-Ion Safety Precautions
Every lithium-ion battery pack should have a safety
circuit which monitors the charge and discharge of the
pack and prevents dangerous occurrences. The
specifications of these safety circuits are dictated by the
cell manufacturer and may include the following:
• Reverse polarity protection
• Charge temperature must not be charged when
temperature is lower than 0°C or above 45°C.
• Charge current must not be too high, typically below
0.7°C
• Discharge current protection to prevent damage due
to short circuits.
• Protection circuitry for over voltage applied to the
battery terminals.
• Overcharge protection circuitry to stop charge when
the voltage per cell rises above 4.3V.
• Over discharge protection circuitry to stop discharge
when the battery voltage falls below 2.3V (varies
with manufacturer).
• Thermal shutdown protection for the battery if the
ambient temperature is above 100°C.
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October 2007 10
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Micrel, Inc. MIC79110
October 2007 11
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Simple Charger - External Trigger to Reset Charge
Cycle reset
SD
VIN
RSET
SNS
BAT
VIN
GND
Reoc
DEOC
AEOC C
DELAY
0.1µF
Reset charge cycle.
The VIN voltage steps up to a voltage greater than VBAT.
When VIN is below VBAT, the IBAT current is near zero and
the reverse shutoff circuit is turning the charge to the
battery off. The IBAT slowly increases as VIN rises above
VBAT. DEOC is pulled low when the IBAT current is above
the Ieoc current set by REOC. When the DEOC is low, the
shutdown pin is also forced low and helps discharge
CSD. When the VBAT reaches the set voltage, the IBAT
begins to slowly drop. When the IBAT is less than the IEOC
threshold, the DEOC output goes high impedance,
indicating end-of-charge. When an external signal is
applied to the gate, the external NCH pulls the SD and
DEOC pins to ground. This restarts the charging process.
External Trigger to Reset Charger
1. VIN steps up to a voltage greater than VBAT.
2. SD held low by CSD until active high DEOC pulls
shutdown low.
3. DEOC releases SD, resistor pull-up from SD pin,
VIN pulls VSD to VIN.
4. An external signal applied to the gate of the
external NCH pulls SD pin-to-ground.
5. IBAT is near zero (2 to 4µA) because VIN is below
VBAT and the reverse shutoff circuit is turning the
charge to the battery off.
6. IBAT is decreased as VBAT approaches VBAT set
volt-age. IBAT decreases below the DEOC
threshold and DEOC is released high allowing VSD
to go high.
7. External NCH turns part on, after a small delay
IBAT turns on.
8. Active high DEOC pin goes high because of
reverse shutoff. DEOC remains high until IBAT
exceeds DEOC threshold, then goes low.
9. IBAT decreases below (see #5) DEOC threshold.
10. Active low DEOC is high because VIN is below
VBAT and reverse shutoff holds DEOC comparator
off. As VIN increases above VBAT, the reverse
volt-age shutoff turns off, DEOC comparator
becomes active. While IBAT is below DEOC
threshold DEOC active low goes low, when IBAT
exceeds DEOC threshold IBAT goes high.
11. Legitimate Activation of active low DEOC until SD
shuts down part and DEOC AL (active low) goes
high.
Micrel, Inc. MIC79110
October 2007 12
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Signal Diagram
Vin
VSD
Vbat set voltage
Vbat
SD threshold
221
Vgate
45
6
3
Ibattery
78
Active high DEOC pin
9
10 Active low DEOC pin
9
Micrel, Inc. MIC79110
October 2007 13
M9999-102507
Auto Top-Off-Charger - Application Circuit
Lithium-Ion batteries will begin to lose their charge over
time. The MIC79110 can be configured to automatically
recharge the battery if the voltage drops below a certain
voltage. This minimum voltage is set by a resistor divider
at the battery and connected to the SD pin. When the
battery voltage falls below the minimum voltage, the SD
pin is pulled low to start the normal charging process.
4.2 V
V
Bat min
Deoc trip
Batter
y
charging
V
s
I
Battery
V
Battery
V
Bat min
=0.975V
(
R1
R2 +1
)
R
2
=1meg R
1
=
(
V
Bat min
0.975 -1
)
1
R
2
Self discharge
4
1
2
3
Vbat set (4.2V)
Vbat low set
by divider.
Vbat
SD Voltage
1. SD not held low by active high DEOC because
DEOC Comparator’s inputs do not common-mode
to ground. Divider holds SD low so part can
start.
2. SD held low by divider.
3. SD held low by active high DEOC.
4. Divider voltage above SD threshold and DEOC
open.
5. Divider voltage drops below SD threshold and
charging begins again.
Top-Off-Charger with Internal Reset - Application
Circuit
R
2
R
1
3M
1M
LI-ion Battery
SD
VIN
RSET
SNS
BAT
VIN
GND
REOC
DEOC
AEOC
V
IN
This circuit is similar to the auto top off charger circuit
mentioned above except that the DEOC pin is externally
triggered to restart the charging cycle. It still uses the
same resistor divider to set the minimum battery voltage
before the lithium-ion needs to be recharged.
Auto-Shutdown Using Shutdown Pin
The shutdown pin on the MIC79110 can be used to
automatically shutdown the battery charger when the
input voltage rises above a safe operating voltage. To
keep the part from heating up and entering thermal
shutdown, we can connect the shutdown pin to VIN using
a resistor divider. Use the following equation to setup the
maximum VIN.
1
R2
R1
V
(MAX)V
SD
IN
+=
The MIC79110 can be connected to a wall wart with a
rectified DC voltage and protected from over voltages at
the input.
Micrel, Inc. MIC79110
October 2007 14
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Package Information
10-Pin 3mm × 3mm MLF
®
(ML)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2004 Micrel, Incorporated.
